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Lathe - dead centre wont reach the workpiece

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Sacha Yabsley08/08/2019 21:39:16
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Hi all,

i have what is probably a very stupid question. I have a Warco GH1236 lathe and I can’t get the dead centre close enough to engage with the workpiece. Even with the tail stock fully extended it is about 60mm too far away. I can’t slide it any further forward as it is prevent from moving further forward by the saddle. It does not help that the DRO reader is on the side of the saddle and restricts how close the tail stock can get but even without this it would fall short. If I move the saddle forward I am unable to machine to the end of the workpiece.

i have attached a picture to show the gap. Here the tool is positioned so as to be able to machine from the end of the workpiece allmost right to the Chuck. While the photo seems to some a bit of a gap between the tail stock and the saddle this is as close as it gets.

Any help would be greatly appreciated. Is it possible to get a longer dead centre or an extension?

Thanks

Sacha

d8462c78-778a-409b-9d79-e66ac26f3a01.jpeg

JasonB09/08/2019 07:00:31
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That's an easy one to solve if you have spare length in the workpiece. Turn your toolpost through 180 degrees and mount the holder on the right side and have the tool poking out the other end. A revolving ctr will also help as they are longer than dead ctrs.

You may also need to angle the topslide so the handle end does not foul the tailstock

David George 109/08/2019 07:03:54
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Hi you can get an extended revolving center which will help and if you wind the compound slide to the rear which will get you a bit closer and if you either rotate the toolpost to put the tool in the right hand side you should get to the end of the job. Try some of these or all.

David

not done it yet09/08/2019 07:49:41
3229 forum posts
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Can the QCTP be moved across the top slide? Turning the top slide by 90 degrees may be necessary.

Your tool geometry appears less than optimal - the cutter would be far more rigid if it were over the centre line of the cross slide. Every bit of cutter overhang causes extra flexing under load.

JB has several options. Turning between centres might be another option to gain space at the headstock end

Extending the tail stock centre, while a possibility, is not particularly recommended - any extra extension cannot be seen as aiding accuracy - but needs must...

The most obvious move would be to start with a longer workpiece and not machine right to the chuck? Same with turning between centres.

Another alternative is to make/buy and fit a ‘lantern type’ single-tool holder in place of the QCTP. QCTPs are good, but not perfect in all scenarios.

Jed Martens09/08/2019 07:56:58
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I had the same issue when using my warco gh600 for the first time. I found that setting the compound to 45 degrees (which means rotating the toolpost the opposite 45 degrees to compensate) has the effect of moving the cutter forward and to the right. This gave me just enough room to engage the dead-centre without running into the carriage with the tailstock.

Obviously this isn't helpful if you're trying to use the compound for cutting tapers or the like.

Jed

SillyOldDuffer09/08/2019 08:05:30
4587 forum posts
980 photos

Removing the telescopic swarf guard from the leadscrew is another possibility. Even fully compressed they take up a fair amount of space, and stop the saddle getting as close to the headstock as it might.

leadguard.jpg

Whether the guard's worth removing or not depends on how often the obstruction is a problem in practice, I've never had the need myself, either the work is long enough, or Jason's method  does the job.  (Easier for me because I have an ordinary 4-position tool post rather than a QTCP.)

It's rather nice not to have to worry about keeping the leadscrew clean.

Dave

 

Edited By SillyOldDuffer on 09/08/2019 08:07:04

Simon Collier09/08/2019 08:15:27
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297 forum posts
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I have the same problem, with the digital readout cover effectively making the cross slide quite a bit wider. It has been a constant frustration, but the acquisition of a second lathe largely solved the problem. There has never been a situation where switching the tool to the RHS of the toolpost has solved the problem, but angling the topslide away helps some.

JasonB09/08/2019 08:25:12
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I suppose you could always unscrew the scale for the odd occasion when you need that bit of extra length, I done that on the mill when pushing it to the limit of it's capacity.

herbert punter09/08/2019 08:25:38
85 forum posts

I had the same problem with my Warco 285; I moved the DRO to the chuck side of the saddle, a bit of work but definitely worth it.

Bert

Trevorh09/08/2019 08:45:04
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I had the same problem on my Warco 1224 and to over come it I simply turned the top slide to 45 degree and re aligned the QCTP to be square to the work - this allows the saddle closer to the chuck and get the tail stock closer to the work

I also had to grind a 45 degree chamfer on the tail stock casting to get the top slide to travel where I needed it to be

Trevor

Mike Poole09/08/2019 09:00:56
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2039 forum posts
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**LINK**

John Stevenson chose a rather drastic solution but not a problem for a man with his skills.

Mike

Clive Foster09/08/2019 09:04:01
1799 forum posts
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Morse taper extension sleeves can be got for around £15. For practical purposes one would move the centre along by the nominal length of the morse taper. Almost worth considering as a normal fit if you aren't seriously restricted by bed length as it would let you work with the tailstock barrel well retracted for much more of the time. When well extended tailstock barrels on smaller machines are less rigid than one might ideally desire.

+1 for the suggestions to alter the coss-slide angle. Mine lives at 25° as its suits the zero 2 zero thread cutting method. Other folk swear by 30° as the infeed is half the slide travel making tiny cuts easier. Needs a razor sharp tool tho'.

With a DRO system there is little need to have the cross slide parallel to the bed for controlled longitudinal cuts as the DRO tells you where the saddle is. Although the saddle hand wheel is less precise to handle than the cross slide feed screw a bed stop makes it easy to hit the same point each time. A bed stop doesn't need to be fancy. A simple block nipped up so it slides stiffly on the bed can be pushed into position by the saddle (with the tool well clear of the work) and locked up when in the correct place. A micrometer plunger makes life easier but half the time I don't bother with the micrometer on my single stop. Just use it as a dumb block.

A short screw driven fine adjuster plunger does make a stop block usefully easier to use as you can quickly get it close, move the saddle to just so and screw the plunger up against the saddle. A calibrated scale isn't important with a DRO around so any decently hefty fine thread will do. I often use 1/8" BSP for such "shift it a bit" setting screws.

Clive

Neil Wyatt09/08/2019 09:22:22
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Two ideas:

Wind the compound slide back to the left.

Consider using a rotating centre.

Neil

Howard Lewis09/08/2019 11:14:46
2207 forum posts
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As already said, rotate the Toolpost, remove / reposition any guards / DRO.

Keep everything as short as possible, to maximise rigidity.

Use plenty of grease on the dead centre.

Having had a bad experience with a rotating centre with brinelled bearings, I minimise use of the new one, unless absolutely necessary. But that is just me being over cautious!

Howard

Sacha Yabsley10/08/2019 05:31:09
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Thank you all for the detailed and useful replies.

IanH10/08/2019 08:27:34
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John Stevenson’s post briefly mentions something that I have observed having been through the exercise of replacing my Student with an imported machine.

I think there was a huge amount of development based on testing and real life operating experience built into the design of all those old British (and probably EU and US) machines. The imported machines seemingly have all the right bits in all the right places, but they often do not seem to have spotted or understood the subtleties of the designs they are copying that make machines really work.

I am not sure either that the current supply chain is going to result in these subtleties being identified and incorporated in imported machines over time.

having said that, model engineering I think is largely about doing unlikely things with inappropriate equipment and this just becomes one additional factor to challenge your ingenuity. Where there is a will, the model engineer will find a way.

Ian

Edited By IanH on 10/08/2019 08:28:49

Edited By IanH on 10/08/2019 08:29:48

Tony Pratt 110/08/2019 09:13:36
882 forum posts
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Ian,

You are right, as an owner of a new Chinese lathe it looks impressive but already I can see I will have problems getting close to the head stock, it's also apparent that my machine has features from UK/US/German machines so a sort of copy from many sources.

Tony

JasonB10/08/2019 10:06:21
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I suppose the counter to that is back in the day a solid ctr was the most commonly used in the tailstock, today I would say that most use a revolving ctr for the majority of jobs which are around 50mm longer than a solid one so to keep things rigid the tailstocks are made with less overhang.

The wider slotted cross slides on the hobby size benchtop machines that people want and DROs on the side all add to the problem.

There is also the selling point of distance between ctrs, if you can advertise a large distance but keep the bed length down you save a little in the manufacturing costs and gain rigidity.

I don't seem to have a problem getting close to the headstock with my machine, the carrage hits it so that seems quite close enough and the tailstock will reach over the cross slide so easy to use that to support say a flat plate on a faceplate while rough centering.

Edited By JasonB on 10/08/2019 10:08:07

KWIL10/08/2019 10:06:22
3111 forum posts
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It would seem that part of the thinking problem/solution is believing that the top slide must always be at 90 degrees to cross slide.

SillyOldDuffer10/08/2019 10:23:46
4587 forum posts
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Posted by IanH on 10/08/2019 08:27:34:

...

I think there was a huge amount of development based on testing and real life operating experience built into the design of all those old British (and probably EU and US) machines. The imported machines seemingly have all the right bits in all the right places, but they often do not seem to have spotted or understood the subtleties of the designs they are copying that make machines really work.

I am not sure either that the current supply chain is going to result in these subtleties being identified and incorporated in imported machines over time.

...

More likely the market isn't driving a need to add subtleties to a basically effective design. All engineering is a compromise and the average hobbyist values his money far more than expensive extras! Far Eastern suppliers are meeting that demand.

Back in the day, the position of British lathe makers was starkly different. After the Victorian boom rather too many makers were competing in a shrinking market for a type of lathe being steadily replaced by capstan lathes, automatics, numeric control and most recently CNC. Factories no longer wanted massed ranks of manual lathes however good they were. Because designing a new machine tool from scratch is expensive, many makers responded to falling sales by adding features and refinements. Most makers went to the wall. The smart ones stopped selling manual lathes altogether or exploited the educational market (now also gone), or sold manual lathes as a niche product to labs, prototyping workshops, refurbishers and small-run production specialists. All jolly good for us buying second-hand in 2019, but commercially doomed when it mattered because in the main lathe makers were swimming against the tide. Same story in the US and Europe: lathes.co.uk lists hundreds of business failures who once made beautiful equipment that no-one wanted.

Current industrial demand is for multi-axis machine centres, and, even though they have lathe features, the design has advanced so far the machine doesn't look much like great-grandad's Drummond or my Chinese lathe at all. Unfortunately I don't see CNC wonders ever finding their way into a home workshop.

Market forces are both powerful and stupid. Sometimes they work in our favour by driving improvement which is why we have wonderful cars, communications and electronics. Other times conditions favour a race to the bottom, like Love Island on TV. Generally though, making and selling cheap tat tends not to last because there isn't much profit in it. All industrial nations start by making junk, I can remember when 'Made in Japan' was a synonym for rubbish, today Japan is strongly associated with quality. My history books tell me Birmingham was once world famous for gewgaws and cheap guns. The tat phase doesn't last, Birmingham has long since moved on and China will too.

Perhaps one day hobby machines will become excellent. When I first encountered Chinese lathes 30 years ago they had a very poor reputation. Slowly but surely they've improved and recently improvements like brushless motors have been added, presumably to attract customers who may be getting more picky. CNC manufacture offers interesting possibilities to hobby customers. Mass-production is the cheapest way to manufacture but it's expensive to set up in the first place. It only pays when large volumes will be sold, and hobby lathes are not mass-market items. Being general purpose, CNC doesn't have the same start-up overheads as mass-production. This opens the door to affordable low-volume quality production, which might be applied to making hobby tools of advanced design, perhaps in the West. Who knows?

I certainly don't. Not so long ago I suggested pre-Brexit would be a good time to buy a Chinese lathe because I expected the value of the pound to fall (it has,12% against the Euro and about 5% against the Dollar and Yuan), and this would push the cost of imports up. What I didn't predict was President Trump would lean on the Chinese (and Europe) by raising tariff barriers as part of his 'America First' policy or that the Chinese would counter US tariffs by dropping the value of the Yuan to compensate. In the UK this could make Chinese lathes cheaper, or more expensive, or cost no different because the effects balance out. I wonder what Nostrodamus has to say?

Reinforces another view I have about lathes. If you're a newcomer wanting to cut metal and are confused about complicated choices, don't dither and agonise. Any lathe is better than no lathe and owning one is a very good way of finding out what's what. You can always buy another one.

Dave

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